Recently, a micro system structure, i.e., a micro electro mechanical system (MEMS) is used for many products. When the micro system structure is used under atmosphere, in which the structure is exposed to collision of particles such as dust, it is required for the structure to protect from damage of the collision of the particles.
When a film is formed on the micro system structure, the inside stress in the film may cause deformation of the micro system structure so that design of the structure is limited. For example, FIG. 10 shows a micro system structure J2 having a diaphragm J1. The diaphragm J1 is only provided by a thin film. In this structure J2, when compression stress is applied to a part of the thin film diaphragm J1, the diaphragm J1 bends so that the diaphragm J1 is corrugated. Therefore, it is required to design the thin film in such a manner that tensile stress is applied to the thin film diaphragm J1.
In general, a method for protecting the micro system structure J2 is as follows. As shown in FIG. 11A, one method is such that the micro system structure J2 is sealed in a casing J3. Further, another method is such that the micro system structure J2 is sealed by hardening resin material J4, as shown in FIG. 11B. In this case, the micro system structure J2 is inserted into melted resin material J4. Further, as shown in FIG. 11C, gel J5 is applied to the micro system structure J2 so that the structure J2 is protected from outside environment.
However, the above micro system structure cannot be used for detecting environmental temperature and for utilizing chemical reaction caused by environment. This is because the micro system structure is separated from the environment.
Further, to protect the micro system structure J2 with a protection film is as follows. Japanese Patent Application Publication No. H06-216121 discloses a protection film made of a silicon nitride film. U.S. Pat. No. 6,388,310 discloses a protection film made of a silicon oxide film and a silicon nitride film. Japanese Patent Application Publication No. 2001-44190 discloses a protection film made of an organic film and a silicon nitride film. The above protection films improve strength and humidity resistance of the micro system structure. Further, the film has low stress therein.
However, the above protection films do not have high protection function against the collision of particles. Therefore, it is required for the micro system structure to protect from the collision stronger when the micro system structure is mounted in tough circumstance.